massive refactoring for interoperability

dns.go

@@ -0,0 +1,57 @@
+package core
+
+import "net"
+import "sync"
+
+// DNSClient is a V2Ray feature for querying DNS information.
+type DNSClient interface {
+	Feature
+	LookupIP(host string) ([]net.IP, error)
+}
+
+type syncDNSClient struct {
+	sync.RWMutex
+	DNSClient
+}
+
+func (d *syncDNSClient) LookupIP(host string) ([]net.IP, error) {
+	d.RLock()
+	defer d.RUnlock()
+
+	if d.DNSClient == nil {
+		return net.LookupIP(host)
+	}
+
+	return d.DNSClient.LookupIP(host)
+}
+
+func (d *syncDNSClient) Start() error {
+	d.RLock()
+	defer d.RUnlock()
+
+	if d.DNSClient == nil {
+		return nil
+	}
+
+	return d.DNSClient.Start()
+}
+
+func (d *syncDNSClient) Close() {
+	d.RLock()
+	defer d.RUnlock()
+
+	if d.DNSClient != nil {
+		d.DNSClient.Close()
+	}
+}
+
+func (d *syncDNSClient) Set(client DNSClient) {
+	if client == nil {
+		return
+	}
+
+	d.Lock()
+	defer d.Unlock()
+
+	d.DNSClient = client
+}